Evaluation of diclofenac degradation effect in “active” and “non-active” anodes: A new consideration about mineralization inclination

This work investigates the electrochemical oxidation (EO) of diclofenac (DCF) in water with Ti/Ti 4 O 7 , Ti/Ru–Ir, Ti/Sb–SnO 2 and Ti/PbO 2 electrodes. Scanning electron microscope and X-ray diffraction results suggest that Ti/Ti 4 O 7 has porous stacked surface morphology and Ti/Sb–SnO 2 possesses the smallest grain size. Linear sweep voltammetry test results indicate that PbO 2 has the highest oxygen evolution potential, while Ti/Ti 4 O 7 and Ti/Ru–Ir show better oxygen evolution activity. DCF degradation results reveal that PbO 2 possessed the highest DCF removal ( R DCF  = 99.2%) and chemical oxygen demand (COD) removal ( R COD  = 97.0%), the fastest COD degradation rate ( k  = 0.0275 min −1 , R 2  = 0.964), the lowest specific energy consumption ( EC DCF  = 1.81 kWh . g DCF −1 , EC TOC  = 6.90 kWh . g TOC −1 ). The toxicity variation of DCF during EO process on PbO 2 is rise first and then to fall. Considering the differences of the four electrodes in residual, conversion and mineralization aspects, mineralization selectivity ( MS ) was proposed to estimate the mineralization inclination of electrodes during EO process, and PbO 2 displays the strongest mineralization inclination ( MS  = 0.594). In addition, the possible degradation pathway of DCF on PbO 2 electrode indicates a composite behavior of conversion and mineralization. All of them above indicate the promising application potential of PbO 2 in lower concentration pharmaceuticals and personal care products wastewater treatment . Moreover, MS could be employed as a supplementary index to assess the different inclinations of this composite behavior on various electrodes used for electrochemical treatment of organics in later studies.